Ah cool. You're going to make your own saves! :)
"ST" means State. This number represents what state the object is in. So for a tree it could be growing, falling etc. Different objects use this in different ways
"STT" means State Timer. This how long the current state has been running in hundredths of seconds.
"SM" only applies to trees and is either 0 or 1 to show if it's "small" meaning it only grows to half normal size.
Thanks